Fig. 12. Schiøtz tonometer on cornea. Footplate (A) rests on corneal surface supporting weight of tonometer, which raises intraocular pressure to Pt. The plunger (B) sinks into the cornea (C), displacing a volume of aqueous humor until the elasticity of the cornea and the intraocular pressure (P) push back with enough force to prevent further sinking of the plunger.